How to check samsung qwerty mobiles are working properly ?

Type on Screen:

 *#0*#

The Screen shows more details to check the Settings :

1.Red

2.Green

3.Blue

4.Melody

5.Vibration

6.Dimming

7.Camera (back camera)

8.Video (front camera)

9.OTP Test.

0.Sleep

* . L Spk (left Speaker)

1.Red :

 Hit number "1" , then the Phone screen will go Red.

2.Green :

 Hit "2" ,then the screen will go Green.

3.Blue :

Hit "3" , Then the screen shows only Blue Color.

4.Melody :

hit number "4", then the melody music will play on speaker.

Its for speaker test.

5.Vibration:

If you hit number "5" , then vibration mode is active on phone.

Its a Vibration test.

6.Dimming :

If you hit "6" ,then Gradient effect of Red,Blue,Green colors are

dimmed to black color to the bottom of each color.

7.Camera ( back camera )

if you hit button number "7" ,Then phone back camera will be shown,

ordinary camera of mobile .

8.Video ( front camera )

Hit the number "8",then front camera will be activated. you can see you face. :)

9.OTP Test :

Hit the "9" ,then four side arrow buttons are shown in the screen, you can swap arrow buttons in the keypad to check if its working or not.

0.Sleep :

Hit the "*" button ,then the mobile will sleep (Screen goes blank)

* .L Spk.

Hit the "0" , then Left side speaker will play a music. 

If all buttons are working well, then the mobile is working properly.
:)